According to a “selective” (as opposed to “instructive”) model of human language capacity, people come to know more than they experience. The discrepancy between experience and eventual capacity (the “poverty of the stimulus”) is bridged by genetically provided information. Hence any hypothesis about the linguistic genotype (or “Universal Grammar,” UG) has consequences for what experience is needed and what form people's mature capacities (or “grammars”) will take. This BBS target article discusses the “trigger experience,” that is, the experience that actually (...) affects a child's linguistic development. It is argued that this must be a subset of a child's total linguistic experience and hence that much of what a child hears has no consequence for the form of the eventual grammar. UG filters experience and provides an upper bound on what constitutes the triggering experience. This filtering effect can often be seen in the way linguistic capacity can change between generations. Children only need access to robust structures of minimal (“degree-0”) complexity. Everything can be learned from simple, unembedded “domains” (a grammatical concept involved in defining an expression's logical form). Children do not need access to more complex structures. (shrink)

Grodzinsky examines Broca's aphasia in terms of some specific grammatical deficits. However, his grammatical models offer no way to characterize the distinctions he observes. Rather than grammatical deficits, his patients seem to have intact grammars but defective modules of parsing and production.

Not only do grammars have the dual structure that Clahsen discusses but the lexicon contains atomic, unanalyzed items, which would be still more mysterious for single-mechanism models. Forms of be in modern English are listed atomically and this is not a simple function of their morphological richness or of the fact that they move.